This is what in Portuguese we call a "tempest in a glass of water"...
:)
In fact, the problem is simple once you think about how write a
constraint to give you the largest Price. Using the "not" CE will help you
on this matter:
rule "Price Product rule using price length"
when
$s : Product ( $productLength : length > 0)
$price : Price( $priceLength : length <= $productLength )
not Price( length > $priceLength, length <= $productLength )
then
$s.setAmount($s.getAmount() + $price.getAmount());
$s.setLength($s.getLength() - $priceLength.intValue());
modify($s);
end
So the above rule is saying: match a Product with a Price, in a way that
does NOT exist another Price whose length is greater than the matched Price,
but still less or equal to the Product length. In other words, match a
Product with the Price with the greatest length but still less or equal to
the Product length.
Hope it helps.
Regards,
Edson
2007/5/11, Mark Proctor <[EMAIL PROTECTED]>:
Interesting problem, you want dyanmic prioritisation based upon the
value of a field. We have no declarative sugar for this, but it might
make a nice use case. We could allow someone to specify an expression
that determine a value of priority.
salience = ($price.length);
That would allow for some interesting situations. Its unlikely this will
make 4.0 - but the solution interests me enough that if I get bored, I
might just do it ;)
Until that time I think you'll have to use some combination of a
command/semaphore object and additional rules.
Mark
Maxime wrote:
> Hello,
>
> I'm trying to find how to manage priority within a rule. Let me
> explain the problem. I'll try to be as clear as possible but bear with
> me since I am new to rules.
> We have two objects, the Product is the object I'm trying to price and
> the object Price is the one that knows all the prices. Both products
> and prices have fields amount and length. Product amount is
> initialized to 0 and prices are going to determine the product amount
> depending on its length.
>
> Let's see an example :
>
> Product : P -> length = 5, amount = 0
> Price : P1 -> length = 1, amount = 50
> Price : P2 -> length = 3, amount = 100
>
> With this configuration, after asserting the 3 objects to the WM, the
> amount field of Product P should have a value of 200 ( 1*100 + 2*50)
> because the price with the greatest length should be favored over the
> other ones.
>
> Here is the rule I made :
>
> rule "Price Product rule using price length"
> when
> $s : Product (length > 0)
> $price : Price($length: length)
> then
> $s.setAmount($s.getAmount() + $price.getAmount());
> $s.setLength($s.getLength() - $length.intValue());
> modify($s);
> end
>
> This is obviously wrong because it always takes the first asserted
> price object. I don't know how to make a rule which would take the
> amount of the price object with the greatest length in priority.
>
> Any help would be very much appreciated.
>
> Cheers,
>
> Max
>
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>
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Edson Tirelli
Software Engineer - JBoss Rules Core Developer
Office: +55 11 3529-6000
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